This application is a national stage of PCT International Application No. PCT/EP2008/010569, filed Dec. 12, 2008, which claims priority under 35 U.S.C. §119 to German Patent Application No. 10 2008 008 857.9, filed Feb. 13, 2008, the entire disclosure of which is herein expressly incorporated by reference.
The invention relates to an apparatus for connecting a shaft to a rotating component, especially a shaft to a turbine wheel of an exhaust gas turbocharger, and to a method for producing such a connection.
Such connections are conventionally produced with a welded or soldered connection with turbines on the exhaust gas side in an exhaust gas turbocharger. It is however problematic that the pairing of the two materials of the shaft or of the turbine wheel have to be adapted to each other in such a manner that a favorable connection between the shaft and the turbine wheel results, in terms of quality. A conflict of goals often results if the turbine wheel has to be manufactured of a correspondingly thermally resistant material on the one hand, while the shaft itself can be manufactured of a conventional and more cost-efficient material in comparison.
It is therefore one object of the present invention to provide a connection (and a method of the type mentioned above) by which the shaft and the rotating component—in particular the turbine wheel—can be connected in an especially advantageous manner.
This and other objects and advantages are achieved by the connection and the method according to the invention for producing such a connection especially for a turbine wheel of an exhaust gas turbocharger, in which an intermediate component is provided, by which the shaft is indirectly connected to the rotating component (turbine wheel). It is thereby provided that the intermediate component and the rotating component are connected by means of a form-locking and/or force-locking connection, especially a riveted connection. In other words, it is provided according to the invention, not to connect the shaft directly to the rotating component—especially the turbine wheel—, but rather by interposition of an intermediate component, wherein the intermediate component and the rotating component are connected in a form-locking and/or force-locking manner. It is for example possible hereby to form the intermediate component in such a manner or to use such a material for this, that it can be connected very well to the rotating component—especially to the turbine wheel—on the one hand, and on the other hand very well to the shaft.
As connections with partners to be connected, as for example titanium aluminum (TiAL) to steel, can only be welded or soldered in an extremely difficult manner or not at all, such a form-locking connection is particularly suitable to fasten the parts to each other correspondingly. In a further arrangement, it has thereby been shown to be particularly advantageous if the rivet for connecting the intermediate component to the rotating component (turbine wheel) is formed as a stump of the rotating component, which is then formed, for example by means of a suitable die, to a rivet which holds the intermediate component at the rotating component in a form-locking manner. It would likewise also be conceivable to define a rivet by means of rotational welding or the like in the rotating component or turbine wheel, if the material permits.
In a particularly advantageous arrangement of the invention, the intermediate component consists of a heat-resistant and weldable material, in particular of an alloy based on nickel, so that the intermediate component can be connected to the turbine wheel which is hot during operation. So that the turbine wheel itself resists the thermal stresses, it can in particular be manufactured of a heat-resistant or highly heat-resistant material. Titanium aluminum (TiAl) is particularly suitable for this purpose.
The intermediate component is preferably connected to the shaft by means of a welded connection, in particular by friction welding or EB (electron beam) welding in a further embodiment of the invention. Especially with one—with regard to the diameter of the components to be connected—radial outward welded connection, a particularly favorable heating results by the friction welding, so that the intermediate component is connected to the shaft in a particularly reliable manner.
Material pairs and constructive embodiments for the turbine wheel and constructive embodiments, with which the rigidity of the connection during the heating by a possibly different heat expansion increases or at least is not reduced, are particularly advantageous.
The advantages described previously in connection with the connection described above are also valid in the same manner for the method according to the invention. This is further distinguished in that the intermediate component is first connected to the rotating component (turbine wheel) by means of the form-locking connection, in particular the riveted connection. The connection technology of heat riveting is particularly suitably for this purpose. In the second method step of the invention of the presently described version of method, the intermediate piece is then correspondingly welded to the shaft, in order to realize the indirect connection of the rotating component (turbine wheel) with the shaft.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.